1. Field of the Invention
The present invention relates to a delivery unit arranged in a surge chamber of a fuel tank of a motor vehicle having a fuel pump for delivering fuel to an internal combustion engine of the motor vehicle, an ejector connected to the fuel pump for the delivery of fuel from the fuel tank to the surge chamber, and a pump holder for holding the fuel pump in the surge chamber.
2. Description of the Related Art
Delivery units having fuel pumps, ejectors, and pump holders are frequently employed in present-day motor vehicles and are known from practice. The pump holder of the known delivery unit has a two-part configuration, a sealing ring inserted in an opening arranged in the floor region of the surge chamber, and an arm fastened to a cap of the surge chamber. The fuel pump is preloaded against the sealing ring by the arm. The ejector is supplied with fuel by the fuel pump and induces the fuel from the fuel tank through an opening. The ejector is integrated in a housing of the fuel pump.
The known fuel pump and ejector combination represents a component of very complex design. In addition, the ejector makes maintenance work on the fuel pump more difficult.
An object of the present invention is to provide a delivery unit for insertion in a surge chamber of a motor vehicle fuel tank that has a simplified assembly and fitting.
The object is met according to the present invention by configuring the ejector as a structural unit with the pump holder and/or the surge chamber.
The inventive configuration allows the fuel pump to be simply fitted in and removed from the surge chamber separately from the ejector. According to the present invention, maintenance work on the fuel pump is not hindered by the ejector and is therefore very simple. Furthermore, the inventive configuration allows the fuel pump to have a simple construction and accordingly, may be manufactured at favorable cost. A further advantage of the present invention is that the materials are separated into their correct types during the removal of the delivery unit according to the invention because the pump holder, like the ejector and the surge chamber, is generally manufactured from plastic and the fuel pump usually exhibits a housing cap and a housing cover made of metal.
The fitting of the delivery unit according to the present invention may comprise a snap-in connection to connect the fuel pump to the pump holder which is fastened onto the floor of the surge chamber. The snap-in connection obviates the need to preload the fuel pump by an arm supported on the cap of the surge chamber.
The fuel pump is reliably held in its specified position if the pump holder exhibits a peripheral rim surrounding a lower region of the fuel pump and the snap-in connection exhibits a protrusion which extends radially inward proximate the free end of the rim.
The fitting and removal of the delivery unit according to the present invention is further simplified if a connection of the pump holder to the floor of the surge chamber is configured as a positive connection.
The ejector may be configured in one piece with the pump holder. However, the ejector exhibits a nozzle and a mixing tube at a distance from the nozzle which complicates the configuration of the pump holder. In accordance with another embodiment of the present invention, the pump holder may be particularly easily manufactured if the floor of the surge chamber exhibits a partial region of a mixing tube of the ejector.
In accordance with another embodiment of the invention, one half of a nozzle and the mixing tube of the ejector are respectively arranged in the surge chamber and the other halves of the nozzle and mixing tube are arranged in the pump holder. Due to this configuration, the ejector is longitudinally split and may, therefore, together with the surge chamber and the pump holder, be simply manufactured by injection casting with axial removal from the molds a particularly cost-favorable configuration.
The inventive design may be further simplified if the ejector is positively connected to the pump holder.
The ejector may, for example, exhibit a branch arranged in the region of an outlet duct leading to the internal combustion engine. Because, however, the internal combustion engine of the motor vehicle requires a higher pressure than the ejector, a branch so arranged requires a cost-intensive pressure-reducing valve arranged. The requirement for a cost-intensive pressure-reducing valve is obviated if the fuel pump is embodied as a peripheral pump or a side channel pump and if a nozzle of the ejector is connected to a branch arranged in the central region of a delivery chamber of the fuel pump. In this arrangement, the branch is arranged at a location in the fuel pump at which the pressure adjusts automatically to the specified pressure.
In a further advantageous embodiment, the ejector is supplied with fuel via its own pump stage. This additional pump stage may be arranged, in a particularly low-cost manner, in the rotor of the main pump stage in a peripheral pump or side channel pump.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.